Internal combustion engines, including diesel engines, gasoline engines, gaseous fuel-powered engines, and other engines known in the art exhaust a complex mixture of air pollutants. These air pollutants are composed of gaseous compounds, such as the oxides of nitrogen (“NOX”), the oxides of sulfur (“SOx”), CO, CO2, NH3, and soot (particulate matter or “PM”). Due to increased awareness of the environment, exhaust emission standards have become more stringent, and the amounts of many of these pollutants emitted from an engine may be regulated depending on the type of engine, size of engine, and/or class of engine.
One method that has been implemented by engine manufacturers to comply with the regulation of engine exhaust pollutants has been to detect different parameters of the exhaust gas (e.g., pressure), and then treat the exhaust gas through various reduction, conversion, and trapping processes based on the detected parameters. Many different types of parameter sensors are currently available for this use. Common sensors used to detect pressure include thermal, ionization, piezoelectric, electromagnetic, and optical pressure sensors. Although functional, some of these architectures may have problems in exhaust gas environments, as their sensing mechanisms can be fouled by soot in the exhaust gas.
One attempt to improve gas pressure detection is described in U.S. Patent Application Publication No. 2011/0128010 (the '010 publication) of Gianchandani et al. The '010 publication is directed toward microdischarge-based pressure sensors that includes an anode, one or more cathodes, a drive circuit connected to the anode and cathode(s), and a measurement circuit that permits sensing of transient current pulses flowing between the anode and cathode(s). In the dual cathode embodiment, one of the cathodes is interposed between the anode and another cathode, and it includes a central opening that permits a microdischarge to occur between the anode and each cathode in response to applied voltage pulses from the drive circuit. Changes in relative current between the two cathodes are measured and used to indicate changes in ambient pressure in the microdischarge chamber. In other embodiments, one of the cathodes acting as a diaphragm, which deflects based on external pressure to change its inter-electrode spacing, thereby altering the relative cathode currents.
There may be limitations to the '010 publication's approach that may inhibit commercialization. For example, the '010 publication advocates monitoring a cathode current to determine changes in pressure, and monitoring current can be problematic. In particular, the current pulses in the '010 publication are generally less than 50 nanoseconds and such short pulses generally require custom built current transformers in order to generate accurate current measurements. Additionally, the current signal may be weak, making it difficult to distinguish from electrical noise in the system.
The pressure detection system of the present disclosure addresses one or more of the problems set forth above and/or other problems of the prior art.